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The role of the copper retainer in alleviating the tendency towards liqua- tion cracking can be related to its effect as a heat sink that reduces the level of superheating andpotentially introduces compressive thermal stresses in the Al- loy 825 HAZ. © 2017 ASME: First published in the Proceedings of the ASME 2017 Pressure Vessels and Piping Conference, PVP2017, July 16-20, 2017, Waikoloa, Hawaii, United States.

Figure 8a: A crack-free tube-to-tubesheet weld completed using the in-bore copper weld retainer. Figure 8b: The penetration Alloy 625 weld metal along grain boundaries in the HAZ of Alloy 825.

References 1 Lippold JC, 1983: An investigation of heat affected zone hot cracking in Alloy 800. Welding Journal, 62(1): 1s–11s. 2 Ramirez AJ and Lippold JC, 2004: High temperature cracking in nickel-base weld metal, Part 2 – Insight into the mecha- nism. Materials Science and Engineering A 380: 245-258. 3 DuPont JN, Lippold JC and Kiser SD, 2009: Welding metal- lurgy and weldability of nickel-base alloys; John Wiley & Sons, Inc. pp. 118-143. 4 Lippold JC, BaeslackWA andVarol I, 1992: Heat affected zone liquation cracking in austenitic and duplex stainless steels. Welding Journal, 71(1): 1s– 14s. 5 Thompson R andGenculu S, 1983: Microstructural evolution in the HAZ of Inconel 718 and correlationwith the hot ductil- ity test. Welding Journal, 62(12): 337s-345s. 6 Pepe JJ and SavageWF, 1967: Effects of constitutional liqua-

tion in 18-Ni maraging steel weldments. Welding Journal, 46(9): 411s-422s. 7 Kelly TJ, 1990: Welding metallurgy of investment cast nickel based super alloys. Trends inWelding Research I, ASM Inter- national, Materials Park, OH, pp. 151-157. 8 Lundin CD, Qiao CYP and Swindeman RW, 1993: HAZ hot cracking behaviour of HD 556 and Inconel 617. International Trends in Welding Science and Technology, ASM Interna- tional, Materials Park, OH, pp. 801-806. 9 Noecker FF andDuPont JN, 2009: Metallurgical investigation into ductility-dip cracking in Ni-based alloys. Part I, Welding Journal, 88(1) 7s-20s. 10 Noecker FF andDuPont JN, 2009: Metallurgical investigation into ductility-dip cracking inNi-based alloys. Part II, Welding Journal, 88(3) 62s-77s.

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